Scholarly Works, Entomology
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Browsing Scholarly Works, Entomology by Subject "0501 Ecological Applications"
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- Drosophila suzukii (Diptera: Drosophilidae) oviposition and adult emergence in six wine grape varieties grown in VirginiaShrader, Meredith Edana; Burrack, Hannah J.; Pfeiffer, Douglas G. (2018-10-01)Drosophila suzukii (Matsumura) is a pest of small fruits and grapes in the United States and in its home range of Japan. Physiological and morphological laboratory testing was performed on six commonly grown wine grape varieties in Virginia. Skin thickness, penetration force, and ºBrix were analyzed to determine ovipositional preferences. Experiments were performed for three consecutive years from grapes collected at one Virginia vineyard. More eggs were laid in intact Viognier grapes than any other variety. Oviposition into intact grapes was not affected by skin thickness or ºBrix; however, oviposition increased when penetration force decreased. An ovipositional choice test determined no varietal preferences. Survivorship from egg to adulthood using uninjured and injured grapes was also assessed to determine varietal suitability as D. suzukii hosts, with more flies emerging from injured grapes than uninjured. However, D. suzukii adults did emerge from intact grapes and at higher percentages than previously recorded in other wine grape studies. All varieties had eggs oviposited into them when injured. Determining the time at which each grape variety became susceptible to oviposition was determined using a D. suzukii bioassay spanning 12 wk using grapes from the green pea stage until ripe. Susceptibility to D. suzukii oviposition was based upon ripening period and penetration force. Early ripening varieties may be more susceptible to D. suzukii oviposition in the field with later maturing, harder fleshed-varieties which may escape D. suzukii oviposition.
- Sweet Corn Sentinel Monitoring for Lepidopteran Field-Evolved Resistance to Bt ToxinsDively, G. P.; Kuhar, Thomas P.; Taylor, Sally V.; Doughty, H. B.; Holmstrom, K.; Gilrein, D.; Nault, B. A.; Ingerson-Mahar, J.; Whalen, J.; Reisig, D.; Frank, Daniel L.; Fleischer, S. J.; Owens, David; Welty, C.; Reay-Jones, F. P. F.; Porter, P.; Smith, J. L.; Saguez, J.; Murray, S.; Wallingford, A.; Byker, H.; Jensen, B.; Burkness, E.; Hutchison, W. D.; Hamby, K. A. (Oxford University Press, 2021-02-01)As part of an insect resistance management plan to preserve Bt transgenic technology, annual monitoring of target pests is mandated to detect susceptibility changes to Bt toxins. Currently Helicoverpa zea (Boddie) monitoring involves investigating unexpected injury in Bt crop fields and collecting larvae from non-Bt host plants for laboratory diet bioassays to determine mortality responses to diagnostic concentrations of Bt toxins. To date, this monitoring approach has not detected any significant change from the known range of baseline susceptibility to Bt toxins, yet practical field-evolved resistance in H. zea populations and numerous occurrences of unexpected injury occur in Bt crops. In this study, we implemented a network of 73 sentinel sweet corn trials, spanning 16 U.S. states and 4 Canadian provinces, for monitoring changes in H. zea susceptibility to Cry and Vip3A toxins by measuring differences in ear damage and larval infestations between isogenic pairs of non-Bt and Bt hybrids over three years. This approach can monitor susceptibility changes and regional differences in other ear-feeding lepidopteran pests. Temporal changes in the field efficacy of each toxin were evidenced by comparing our current results with earlier published studies, including baseline data for each Bt trait when first commercialized. Changes in amount of ear damage showed significant increases in H. zea resistance to Cry toxins and possibly lower susceptibility to Vip3a. Our findings demonstrate that the sentinel plot approach as an in-field screen can effectively monitor phenotypic resistance and document field-evolved resistance in target pest populations, improving resistance monitoring for Bt crops.